Hydraulic control for self-loading scraper with three-speed elevator drive

ABSTRACT

A hydraulic control system for a self-loading scraper elevator drive having a plurality of pumps for combined control of the scraper bowl, ejector, and elevator drives, the flow from the pumps being selectively combinable under the control of an operator to vary the speed of the elevator drive to accommodate different conditions of machine operation. The system permits more efficient utilization of the available engine torque which must be used for propelling the vehicle and driving the scraper bowl, ejector and elevator.

United States Patent Junck et al.

[ Jan. 15, 1974 HYDRAULIC CONTROL FOR SELF-LOADING SCRAPER WITHTHREE-SPEED ELEVATOR DRIVE Inventors: John A. Junck, Joliet, 111.;Joseph Kokaly, Buckeye, Ariz.

Assignee: Caterpillar Tractor Co., Peoria, 111.

Filed: Dec. 27, 1971 Appl. No.: 212,136

U.S. Cl 60/421, 60/471, 91/414 Int. Cl. F1611 39/48 Field of Search60/52 HE, 375, 421,

References Cited UNITED STATES PATENTS 12/1937 Henry 60/421 X 3/1942Vosseler et a1 60/53 R UX 2,879,612 3/1959 Schultz at al 611/52 Hli X3,258,926 7/1966 Junck et a1..., 60/52 HE X 3,443,380 5/1969 Karazija60/52 HE Primary Examiner-Edgar W. Geoghegan Attorney-Leonard Phillips[57] ABSTRACT 3 Claims, 1 Drawing Figure 3 RESERV O HYDRAULIC CONTROLFOR SELF-LOADING SCRAPER WITH THREE-SPEED ELEVATOR DRIVE BACKGROUND OFTHE INVENTION In recent years elevating self-loading scrapers have beendeveloped into production tools which are required to handle a varietyof materials from rock and relatively undisturbed soils to more'easilyhandled materials such as sand and windrows. As a result the de mands onthe drive mechanism of these self-loading scrapers have resulted in theadvent of electric and hydraulic drives for more rugged and dependableoperation as well as greater flexibility and simplicity in providing thecorrect elevator speeds.

As the use of the self-loading scraper has been extended to aconsiderable variety of materials, the torque requirements forpropelling the vehicle and for driving the elevator varies with eachmaterial encountered. For example, when loading extremely strongundisturbed materials, a considerable amount of torque is required topropel the machine along the ground in view of the resistance tomovement of the scraper cutting edge through the material being loaded.This dictates that a large portion of the available torque be directedto the tractor wheels to maintain movement of the vehicle.

When loading rocks it is necessary that the resistor be driven ratherslowly such that the impact of the flights on the rocks will not resultin forces damaging or destroying the elevator construction. When thescraper is used for the loading of average or light materials the torquerequirement for propelling the vehicle is less severe. Therefore, moreof the torque may be used to drive the elevator with the result that ahigher speed drive and thus increased loading efficiency may beachieved.

When the scraper is used for loading sand, windrows, and other easilyhandled materials, a substantial portion of the available torque may beused for driving the elevator, thus permitting it to be operated at asubstantially higher speed to increase the rate of loading. Therefore itis desirable that an elevator drive be provided which will permit theoperator to select the elevator speed most compatible with theconditions under which the scraper is being operated.

SUMMARY OF THE INVENTION The present invention relates to an improvedhydraulic control system for self-loading scrapers of the elevatingtype, and more particularly to a combined control system wherein threepumps are used for supply of fluid to the circuit to control the scraperbowl and ejector drives as well as to provide three speeds of elevatordrive.

In the accomplishment of the foregoing and other advantages andfeatures, the control system of the present invention generally includesa control valve for selectively channeling the flow of fluid from a pumpto the scraper bowl and ejector drives to effect bowl lift and ejectoroperations, and for selectively combining and channeling the fluid flowsfrom such pump and two additional pumps to the elevator drive to effectselectable speed control of the elevator.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a schematic fluidcircuit diagram of a hydraulic control system in accordance with thepresent invention, a control valve of the system being shown inelevation with portions broken away.

DETAILED DESCRIPTION OF THE INVENTION Considering now the invention indetail and referring to the illustrated form thereof in the drawing,there will be seen to be provided a hydraulic control system forselectively controlling the operations of the bowl, ejector, andelevator drives of an elevating self-loading scraper.

The bowl drive includes the usual pair of bowl lift jacks 11 for raisingor lowering the: bowl in accordance with the direction of fluid flow toand from the opposite ends of the jack cylinders. The ejector drivecomprises an ejector jack 12 for operating or retracting the ejectordepending upon the direction of fluid flow to and from the ends of thejack cylinder in a conventional manner. The elevator drive comprises ahydraulic motor 13 coupled to the elevator to drive same at a speeddetermined by the volume of fluid flow through the motor.

The control system basically includes a plurality of pumps 14, 16 and 17and a three-spool control valve 18, or equivalent means for selectivelychanneling the flow of output fluid from the pumps to the bowl jacks ll,ejector jack 12, and elevator drive motor 13. More particularly, thevalve comprises a body 19 having three parallel bores 21, 22 and 23 forreciprocably housing bowl, ejector and elevator speed control spools 24,26 and 27. The vlave body is provided with inlet ports 28, 29 and 31, afluid return port 32, and control ports 33, 34 and 36.

The pump 14 is adapted to draw fluid from reservoir 37 for supplythrough a conduit 38 to inlet port 28, and the return port 32 isconnected via conduit 39 to the reservoir. Pumps 16 and 17 are likewiseadapted to draw fluid from reservoir 37 for supply through conduits 41and 42 to inlet ports 29 and 31.

Inlet port 28 is communicated with a central portion 43 of bore 21, inturn communicated with a central portion 44 of bore 22 by means of abifurcated passage 46. A bifurcated passage 47 communicates the centralportion 44 of bore 22 with a central portion 48 of bore 23, and centralportion 48 communicates with return port 32 via a passage 49.

First end portions 51, 52 and 53 of bores 21, 22 and 23 are commonlycommunicated with return passage 49 by means of an interconnectingpassage 54, and a passage 56 commonly communicates second opposite endportions 57, 58 and 59 with passage 49.

Inlet port 29 is communicated with an intermediate portion 61 of bore 23disposed between central portion 48 and the second end portion 59thereof. Inlet port 31 is communicated with an intermediate portion 62of bore 23 disposed between the first end portion 53 and central portion48 thereof.

Bore 21 is similarly provided with portions 63 and 64 respectivelyintermediate central portion 43 and opposite end portions 51 and 57, andbore 22 is provided with portions 66 and 67 respectively intermediatecentral portion 44 and opposite end portions 52 and 58. Intermediatebore portions 64 and 67 are commonly communicated with control port 33via an interconnecting passage 68. Intermediate bore portions 63 and 66are respectively communicated with control ports 34 and 36.

Control port 33 is then commonly connected by means of conduit 69 to oneend of the cylinders of bowl jacks 11 and one end of the cylinder ofejector jack 12. Control port 34 is connected via conduit 71 to thesecond ends of the cylinders of the bowl jacks, and control port 36 isconnected via conduit 72 to the second end of the cylinder of theejector jack.

With regard to the connections of the elevator drive motor 13 to thehydraulic control system, it is to be noted that the supply conduit 41from pump 16 is connected to the inlet port of the motor by means of aconduit 73 and check valve 74. The inlet port of the motor 13 is alsoconnected via conduit 76 to the supply conduit 42 of pump 17. The outletport of the motor is connected via conduit 77 to the reservoir 37. Areleif valve 78 is paralleled with the motor and a relief valve 79 isparalleled with pump 14 to limit maximum pressure in the elevator drivecircuit and in the bowl and ejector control portion of the circuit.

Considering now the control spools 24, 26 and 27 in more detail, it isto be noted that same are appropriately configured to control the flowof fluid from the pumps 14, 16 and 17 through the valve 18 to theelevator motor 13 and bowl and ejector jacks 11 and 12 in accordancewith the positions of the spools in the bores 21, 22 and 23.

More particularly, bowl control spool 24 is of such a configuration thatin a neutral position (N) thereof, as shown in the drawing,communication is permitted between inlet port 28 and central portion 43of bore 21, as well as between such central portion and passage 46leading to central portion 44 of bore 22. At the same time,communication is blocked between central portion 43 and intermediateportions 63 and 64, as well as between the intermediate portions 63 and64 and respective end portions 51 and 57.

Ejector spool 26 is similarly configured such that in a neutral position(N) thereof, as shown in the drawing, communication is permitted betweenpassage 46 and central portion 44 of bore 22, and between centralportion 44 and passage 47. At this time communication is blocked betweencentral portion 44 and intermediate portions 66 and 67 of bore 22, aswell as between such intermediate portions and end portions 52 and 58.

Elevator spool 27 is of a configuration such that in a neutral position(N) thereof, as shown in the drawing, communication is permitted betweencentral porition 48 of bore 23 and passages 47 and 49. Communication issimultaneously blocked between central portion 48 and intermediateportions 61 and 62. However, communication is permitted betweenintermediate portion 61 and end portion 59 and between intermediateportion 62 and end portion 53.

It will be thus appreciated that with all of the spools 24, 26 and 27 inneutral position, pump 14 returns fluid to reservoir 37 via a pathincluding inlet port 28, central portion 43 of bore 21, passage 46,central portion 44 of bore 22, passage 47, central portion 48 of bore23, passage 49, return port 32, and conduit 39. Pump 16 returns fluid toreservoir 37 via a path comprising inlet port 29, intermediate and endportions 61 and 59 of bore 23, passage 49, return port 32 and conduit39. Pump 17 returns fluid to reservoir 37 via a path comprising inletport 31, intermediate and end portions 62 and 53, passage 49, returnport 32 and conduit 39. Consequently, the valve 18 diverts the outputflows from pumps 14, 16 and 17 directly to reservoir 37 and away fromthe hydraulic drives for the bowl, ejector, and elevator, when thespools are in their neutral positions.

The configuration of the bowl control spool 24 is further arranged suchthat in a raise position (R) thereof shifted to the right from theposition depicted in the drawing, communication is blocked between inletport 28 and central portion 43 of bore 21, while communication isestablished between such port and intermediate portion 63. Communicationis still blocked between intermediate portion 63 and end portion 51, butcommunication is established between intermediate portion 64 and endportion 57.

With the spools 26 and 27 in their neutral positions, flow is at thistime effected from pump 14 to the appropriate ends of bowl lift jacks 11to produce raising of the bowl, while flow is effected from the oppositeends of the jacks to the reservoir 37.

More particularly, the output supply of fluid from pump 14 flows via apath including conduit 38, inlet port 28, intermediate portion 63 ofbore 21, control port 34, and conduit 71 to the lower ends of the jacks11. The upper ends of the jacks are communicated with the reservoir 37via a path comprising conduit 69, control port 33, intermediate portion67 of bore 22, passage 68, intermediate and end portions 64 and 57 ofbore 21, passages 56 and 49, return port 32 and conduit 39.

When the control spool 24 is moved to a lower posi tion (L) shifted tothe left from the position depicted in the drawing, communication isblocked between inlet port 28 and central portion 43, whilecommunication is established between the inlet port and intermediateportion 64. Communication is blocked between intermediate portion 64 andend portion 57, while communication is established between intermediateportion 63 and end portion 51. As a result, flow is established frompump 14 to the upper ends or lift jacks 11, while flow is establishedfrom the lower ends thereof to the reservoir 37 to thereby effectlowering of the bowl.

In this regard, the output supply of fluid from pump 14 flows via a pathincluding conduit 38, inlet port 28, intermediate portion 64 of bore 21,passage 68, intermediate portion 67 of bore 22, control port 33, andconduit 69 to the upper ends of the jacks 11. The lower ends of thejacks are communicated with the reservoir 37 via a path comprisingconduit 71, control port 34, intermediate and end portions 63 and 51 ofbore 21, passages 54 and 49, return port 32 and conduit 39.

The configuration of ejector spool 26 is also arranged such that in theretract position (R) shifted to the right from the position depicted inthe drawing, communication is blocked between passage 46 and centralportion 44 of bore 22. Communication is at this time established betweenpassage 46 and intermediate portion 66 of bore 22, while communicationis blocked between passage 46 and intermediate portion 67. Communicationis blocked between intermediate and end portions 66 and 52, andestablished between intermediate and end portions 67 and 58.

Thus, in the retract position of spool 26, spools 24 and 27 being intheir neutral positions, the output supply of fluid from pump 14 flowsvia a path comprising conduit 38, inlet port 28, central portion 43 ofbore 21, passage 46, intermediate portion 66 of bore 22, control port36, and conduit 72 to a first end of ejectorjack 12. At the same time,the second end ofjack 12 is communicated with reservoir 37 via a pathcomprising conduit 69, control port 33, intermediate and end portions 67and 58 of bore 22, passages 56 and 49, return port 32, and conduit 39.As a result, the jack 12 retracts the ejector.

In response to movement of the spool 26 to an eject position (E) shiftedto the left from the position depicted in the drawing, communication isblocked between passage 46 and central portion 44 of bore 22.Communication is established between passage 46 and intermediate portion67 of bore 22, while communication is blocked between passage 46 andintermediate portion 66. Communication is established betweenintermediate and end portions 66 and 52, while communication is blockedbetween intermediate and end portions 67 and 58. Consequently, theoutput supply of fluid from pump 14 flows via a path defined by conduit38, inlet port 28, central portion 43 of bore 21, passage 46,intermediate portion 67 of bore 22, control port 33, and conduit 69 tothe second end of jack 12. The first end of jack 12 is communicated withreservoir 37 via a path comprising control port 36, intermediate and endportions 66 and 52 of bore 22, passages 54 and 49, return port 32, andconduit 39. The flow conditions are thus such as to effect an ejectstroke of the ejector.

[t is to be noted that the elevator spool 27 is arranged to providethree speeds of the elevator motor 13 responsive to the spool beingrespectively in low (L), medium (M), and high (H) speed positions. Whenthe spool is in the low speed position, communication is permittedbetween central portion 48 of bore 23 and passages 47 and 49.Communication is blocked between intermediate portion 62 and passage 47and end portion 53. Communication is blocked between intermediateportion 61 and passage 47, while communication is established betweenintermediate portion 61 and end portion 59.

With the bowl and ejector spools 24 and 26 in neutral position, theoutput supply of fluid from pump 14 is returned to reservoir 37 via apath defined by conduit 38, inlet port 28, central portion 43 of bore21, passage 46, central portion 44 of bore 22, passage 47, centralportion 48 of bore 23, passage 49, return port 32, and conduit 39. Theoutput supply of fluid from pump 16 is returned to reservoir 37 via apath comprising conduit 41, inlet port 29, intermediate and end portions61 and 59 of bore 23, passage 49, return port 32 and conduit 39.

However, at the same time, communication between pump 17 and reservoir37 is interrupted by virtue of spool 27 blocking portion 62 of bore 23from portion 53. Under these conditions, the output of pump 17 isredirected through conduits 76 and 73 from where it flows through motor13, effecting relatively slow speed drive of the elevator, and isdischarged from the motor through conduit 77 to reservoir 37. Thisresults in a minimum of the available torque being used to drive theelevator such that sufficient torque is available to the tractor wheelsfor propelling the vehicle. Such distribution of torque is desirablewhen loading relatively strong materials and/or rocks where considerabletorque is required for propelling the vehicle, or when relatively highflight speed might result in damage to the elevator.

The medium speed position of spool 27 establishes flow conditions whichare particularly appropriate when the scraper is used for the loading ofaverage soils and the torque requirements for driving the elevator andpropelling the machine permit the use of a somewhat higher elevatorspeed to achieve the maximum loading rate.

More particularly, when the spool 27 is in the medium speed position,communication is still blocked between intermediate and end portions 62and 53, and communication is still permitted between central portion 48and passages 47 and 49. However, communication is now blocked betweenintermediate and end portions 61 and 59. Thus, as in the case of the lowspeed position of the spool, the output of pump 17 is redirected throughmotor 13, while the output of pump 14 is returned to the reservoir 37via the same flow path previously described. However, in addition, theoutput of pump 16 is now blocked from the reservoir and is redirectedthrough check valve 74 and conduit 73 where it is combined with thedischarge volume of pump 17 to effect medium speed drive of elevatormotor 13.

When the scraper is used for loading sand, windrows, or other easy toload materials, the torque requirements of propelling the vehicle arerelatively low such that the speed of the elevator may be increased. Thehigh speed position of spool 27 establishes flow conditions to theforegoing ends. In this regard, when the spool is in the high speedposition, it maintains the conditions hereinbefore described for mediumspeed and in addition blocks communication between passage 47 andcentral portion 48 of bore 23 and establishes communication betweenpassage 47 and intermediate portion 61 of bore 23. Under theseconditions the discharge volume from pump 14 flows via the pathpreviously described as far as passage 47 whereat it is diverted viabore portion 61 to port 29 and conduit 41 for combination with theoutput volume of pump 16. These combined volumes flow through checkvalve 74 to conduit 73 where they are combined with the output of pump17 with the total volume of all three pumps being directed through motor13 to effect high speed drive of the elevator.

Under the conditions just described, should either of spools 24 or 26 beactuated to one of the operative positions to divert the volume of pump14 to the bowl lift jacks 11 or ejector jack 12, the fluid returningfrom the opposite ends of the actuated jacks is returned to reservoir 37by way of one or the other of passages 54 or 56, passage 49, return port32 and conduit 39.

This results in the speed of motor 13 being reduced to that provided bythe combined volumes of pumps 16 and 17, or, in other words, the samespeed as that provided with spool 27 in the previously described mediumspeed position. It should be noted that when spool 27 is in either ofthe medium or low speed positions, actuation of spools 24 and 26 doesnot affect the speed at which motor 13, and hence the elevator, isdriven.

Although the invention has been hereinbefore described and illustratedin the accompanying drawing with respect to a single preferredembodiment, it will be appreciated that various modifications andchanges may be made therein without departing from the true spirit andscope of the invention, and thus it is not intended to limit theinvention except by the terms of the appended claims.

I claim:

1. A multiple speed hydraulic drive for an elevating self-loadingscraper comprising a. hydraulic elevator drive motor, a fluid reservoir,at least three pumps communicating with said reservoir and having outletsides communicably coupled to a first side of said motor, meanscommunicably coupling a second side of said motor to said reservoir, andvalve means coupled between said outlet sides of said pumps and saidreservoir and operable by movement of a single valving element thereofto selectively divert the fluid flows thereof from said first side ofsaid motor to said reservoir whereby flow from one pump may beselectively supplied to said motor to drive said motor at one speed,flow from another pump may be selectively supplied to said motor inaddition to said flow from said one pump to drive said motor at another,higher speed, and flow from the other pump may be selectively suppliedto said motor in addition to said flows from said one and said anotherpumps to drive said motor at another, still higher speed.

2. A hydraulic control for an elevating self-loading scraper comprisingbowl lift hydraulic jacks having first and second ends for inlet oroutlet of fluid, an ejector hydraulic jack having first and second endsfor inlet or outlet of fluid, an elevator hydraulic drive motor havingfirst and second sides respectively for inlet and outlet of fluid, afluid reservoir, means communicating said second side of said motor withsaid reservoir, first, second, and third pumps having inlet sidescommunicated with said reservoir and having outlet sides, meanscommunicably connecting said outlet sides of said second and third pumpsto said first side of said motor, and a spool control valve includingbowl, ejector, and elevator speed control spools and having first,second, and third inlet ports, a fluid return port, and first, second,and third control ports, said bowl lift spool having se lectableneutral, raise, and lower positions, said ejector spool havingselectable neutral, eject, and retract positions, said elevator spoolhaving selectable neutral, low, medium, and high speed positions, saidoutlet sides of said first, second, and third pumps respectivelycommunicably connected to said first, second, and third inlet ports,said return port communicably connected to said reservoir, said firstcontrol port communicably connected to said first ends of said bowl liftjacks, said second control port communicably connected to said first endof said ejector jack, said third control port communicably connected tosaid second ends of bowl lift jacks and to said second end of saidejector jack, said valve being arranged to communicate said first,second, and third inlet ports with said return port responsive to saidbowl, ejector, and elevator spools being in said neutral positionsthereof, said valve being arranged to communicate said first inlet portwith said first control port and communicate said third control portwith said return port responsive to said bowl spool being in said raiseposition thereof, said valve being arranged to communicate said firstinlet port with said third control port and communicate said firstcontrol port with said return port responsive to said bowl spool beingin said lower position thereof, said valve being arranged to communicatesaid first inlet port with said second control port and communicate saidthird control port with said return port responsive to said ejectorspool being in said eject position thereof while said bowl spool is insaid neutral position thereof, said valve being arranged to communicatesaid first inlet port with said third control port and communicate saidsecond control port with said return port responsive to said ejectorspool being in said retract position thereof while said bowl spool is insaid neutral position thereof, said valve being arranged to communicatesaid second inlet port with said return port and block communicationbetween said third inlet port and said return port while communicatingsaid first inlet port with said return port responsive to said elevatorspool being in said low speed position thereof while said bowl andejector spools are in said neutral positions thereof, said valve beingarranged to block communication between said second and third inletports and said return port while communicating said first inlet portwith said return port responsive to said elevator spool being in saidmedium speed position thereof while said bowl and ejector jacks are insaid neutral positions thereof, said valve being arranged to blockcommunication between said second and third inlet ports and said returnport while establishing communication between said first inlet port andsaid second inlet port responsive to said elevator spool being in saidhigh speed position thereof while said bowl and ejector spools are insaid neutral positions thereof.

3. A hydraulic control according to claim 2, further defined by saidvalve having a body including said inlet, return, and control ports,said body having a first bore housing said bowl spool for reciprocationtherein between said neutral, raise and lower positions thereof, saidbody having a second bore housing said ejector spool for reciprocationtherein between said neutral, eject, and retract positions thereof, saidbody having a third bore housing said elevator spool for reciprocationtherein between said neutral, low, medium, and high speed positionsthereof, said first, second, and third bores respectively having centralportions, first and second opposite end portions, and first and secondintermediate portions between said central portion and said first andsecond end portions, said first inlet port communicated with saidcentral portion of said first bore, said second and third inlet portsrespectively communicated with said first and second intermediateportions of said third bore, said first and second control portsrespectively communicated with said second intermediate portions of saidfirst and second bores, said third control port communicated with saidfirst intermediate portion of said second bore, said body having apassage communicating said central portions of said first and secondbores, a second passage communicating said central portions of saidsecond and third bores, a third passage communicating said centralportion of said third bore with said return port, a fourth passagecommunicably connecting said first end portions of said first, secondand third bores to said third passage, a fifth passage communicablyconnecting said second end portions of said first, second and thirdbores to said third passage, and a sixth passage communicably connectingsaid first intermediate portions of said first and second bores, saidbowl spool being configured to block communication between said centralportion and first and second intermediate portions of said first bore,block communication between said first and second intermediate portionsand first and second end portions of said first bore, and permitcommunication between said central portion of said first bore and saidfirst passage in said neutral position thereof, block communica tionbetween said first inlet port and said central portion of said firstbore, block communication between said first inlet'port and said firstintermediate portion of said first bore, block communication betweensaid central portion and first intermediate portion of said first bore,block communication between said second intermediate and end portions ofsaid first bore, establish communication between said first inlet portand second intermediate portion of said first bore, and establishcommunication between said first intermediate and end portions of saidfirst bore in said raise position thereof, and block communicationbetween said first inlet port and said central portion of said firstbore, block communication between said first inlet port and said secondintermediate portion of said first bore, block communication betweensaid central portion and second intermediate portion of said first bore,block communication between said first intermediate and end portions ofsaid first bore, establish communication between said first inlet portand first intermediate portion of said first bore, and establishcommunication between said second intermediate and end portions of saidfirst bore in said lower position thereof, said ejector spool beingconfigured to permit communication between said central portion of saidsecond bore and said first and second passages, block communicationbetween said central and first and second intermediate portions of saidsecond bore, and block communication between said first and secondintermediate portions and first and second end portions of said secondbore in said neutral position thereof, block communication between saidcentral portion of said second bore and said first passage, blockcommunication between said central and first and second intermediateportions of said second bore, block communication between said firstintermediate and end portions of said second bore, establishcommunication between said first passage and said first intermediateportion of said second bore, and establish communication between saidsecond intermediate and end portions of said second bore in said ejectposition thereof, and block communication between said central portionof said second bore and said first passage, block communication betweensaid central and first and second intermediate portions of said secondbore, block communication between said second intermediate and endportions of said second bore, cs

tablish communication between said first passage and said secondintermediate portion of said second bore, and establish communicationbetween said first intermediate and end portions of said second bore insaid retract position thereof, said elevator spool being configured topermit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, establishcommunication between said first intermediate and end portions of saidthird bore, and establish communication between said second intermediateand end portions of said third bore in said neutral position thereof,permit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, permitcommunication between said first intermediate and end portions of saidthird bore, and block communication between said second intermediate andend portions of said third bore in said low speed position thereof,permit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, blockcommunication between said first intermediate and end portions of saidthird bore, and block communication between said second intermediate andend portions of said third bore in said medium speed position thereof,and block communication between said central portion of said third boreand said second passage, block communication between said central andfirst and second intermediate portions of said third bore, blockcommunication between said first intermediate and end portions of saidthird bore, block communication between said second intermediate and endportions of said third bore, and establish communication between saidsecond passage and said first intermediate portion of said third bore insaid high speed position thereof.

1. A multiple speed hydraulic drive for an elevating selfloading scrapercomprising a hydraulic elevator drive motor, a fluid reservoir, at leastthree pumps communicating with said reservoir and having outlet sidescommunicably coupled to a first side of said motor, means communicablycoupling a second side of said motor to said reservoir, and valve meanscoupled between said outlet sides of said pumps and said reservoir andoperable by movement of a single valving element thereof to selectivelydivert the fluid flows thereof from said first side of said motor tosaid reservoir whereby flow from one pump may be selectively supplied tosaid motor to drive said motor at one speed, flow from another pump maybe selectively supplied to said motor in addition to said flow from saidone pump to drive said motor at another, higher speed, and flow from theother pump may be selectively supplied to said motor in addition to saidflows from said one and said another pumps to drive said motor atanother, still higher speed.
 2. A hydraulic control for an elevatingself-loading scraper comprising bowl lift hydraulic jacks having firstand second ends for inlet or outlet of fluid, an ejector hydraulic jackhaving first and second ends for inlet or outlet of fluid, an elevatorhydraulic drive motor having first and second sides respectively forinlet and outlet of fluid, a fluid reservoir, means communicating saidsecond side of said motor with said reservoir, first, second, and thirdpumps having inlet sides communicated with said reservoir and havingoutlet sides, means communicably connecting said outlet sides of saidsecond and third pumps to said first side of said motor, and a spoolcontrol valve including bowl, ejector, and elevator speed control spoolsand having first, second, and third inlet ports, a fluid return port,and first, second, and third control ports, said bowl lift spool havingselectable neutral, raise, and lower positions, said ejector spoolhaving selectable neutral, eject, and retract positions, said elevatorspool having selectable neutral, low, medium, and high speed positions,said outlet sides of said first, second, and third pumps respectivelycommunicably connected to said first, second, and third inlet ports,said return port communicably connected to said reservoir, said firstcontrol port communicably connected to said first ends of said bowl liftjacks, said second control port communicably connected to said first endof said ejector jack, said third control port communicably connected tosaid second ends of bowl lift jacks and to said second end of saidejector jack, said valve being arranged to communicate said first,second, and third inlet ports with said return port responsive to saidbowl, ejector, and elevator spools being in said neutral positionsthereof, said valve being arrangEd to communicate said first inlet portwith said first control port and communicate said third control portwith said return port responsive to said bowl spool being in said raiseposition thereof, said valve being arranged to communicate said firstinlet port with said third control port and communicate said firstcontrol port with said return port responsive to said bowl spool beingin said lower position thereof, said valve being arranged to communicatesaid first inlet port with said second control port and communicate saidthird control port with said return port responsive to said ejectorspool being in said eject position thereof while said bowl spool is insaid neutral position thereof, said valve being arranged to communicatesaid first inlet port with said third control port and communicate saidsecond control port with said return port responsive to said ejectorspool being in said retract position thereof while said bowl spool is insaid neutral position thereof, said valve being arranged to communicatesaid second inlet port with said return port and block communicationbetween said third inlet port and said return port while communicatingsaid first inlet port with said return port responsive to said elevatorspool being in said low speed position thereof while said bowl andejector spools are in said neutral positions thereof, said valve beingarranged to block communication between said second and third inletports and said return port while communicating said first inlet portwith said return port responsive to said elevator spool being in saidmedium speed position thereof while said bowl and ejector jacks are insaid neutral positions thereof, said valve being arranged to blockcommunication between said second and third inlet ports and said returnport while establishing communication between said first inlet port andsaid second inlet port responsive to said elevator spool being in saidhigh speed position thereof while said bowl and ejector spools are insaid neutral positions thereof.
 3. A hydraulic control according toclaim 2, further defined by said valve having a body including saidinlet, return, and control ports, said body having a first bore housingsaid bowl spool for reciprocation therein between said neutral, raiseand lower positions thereof, said body having a second bore housing saidejector spool for reciprocation therein between said neutral, eject, andretract positions thereof, said body having a third bore housing saidelevator spool for reciprocation therein between said neutral, low,medium, and high speed positions thereof, said first, second, and thirdbores respectively having central portions, first and second oppositeend portions, and first and second intermediate portions between saidcentral portion and said first and second end portions, said first inletport communicated with said central portion of said first bore, saidsecond and third inlet ports respectively communicated with said firstand second intermediate portions of said third bore, said first andsecond control ports respectively communicated with said secondintermediate portions of said first and second bores, said third controlport communicated with said first intermediate portion of said secondbore, said body having a passage communicating said central portions ofsaid first and second bores, a second passage communicating said centralportions of said second and third bores, a third passage communicatingsaid central portion of said third bore with said return port, a fourthpassage communicably connecting said first end portions of said first,second and third bores to said third passage, a fifth passagecommunicably connecting said second end portions of said first, secondand third bores to said third passage, and a sixth passage communicablyconnecting said first intermediate portions of said first and secondbores, said bowl spool being configured to block communication betweensaid central portion and first and second intermediate portions of saidfirSt bore, block communication between said first and secondintermediate portions and first and second end portions of said firstbore, and permit communication between said central portion of saidfirst bore and said first passage in said neutral position thereof,block communication between said first inlet port and said centralportion of said first bore, block communication between said first inletport and said first intermediate portion of said first bore, blockcommunication between said central portion and first intermediateportion of said first bore, block communication between said secondintermediate and end portions of said first bore, establishcommunication between said first inlet port and second intermediateportion of said first bore, and establish communication between saidfirst intermediate and end portions of said first bore in said raiseposition thereof, and block communication between said first inlet portand said central portion of said first bore, block communication betweensaid first inlet port and said second intermediate portion of said firstbore, block communication between said central portion and secondintermediate portion of said first bore, block communication betweensaid first intermediate and end portions of said first bore, establishcommunication between said first inlet port and first intermediateportion of said first bore, and establish communication between saidsecond intermediate and end portions of said first bore in said lowerposition thereof, said ejector spool being configured to permitcommunication between said central portion of said second bore and saidfirst and second passages, block communication between said central andfirst and second intermediate portions of said second bore, and blockcommunication between said first and second intermediate portions andfirst and second end portions of said second bore in said neutralposition thereof, block communication between said central portion ofsaid second bore and said first passage, block communication betweensaid central and first and second intermediate portions of said secondbore, block communication between said first intermediate and endportions of said second bore, establish communication between said firstpassage and said first intermediate portion of said second bore, andestablish communication between said second intermediate and endportions of said second bore in said eject position thereof, and blockcommunication between said central portion of said second bore and saidfirst passage, block communication between said central and first andsecond intermediate portions of said second bore, block communicationbetween said second intermediate and end portions of said second bore,establish communication between said first passage and said secondintermediate portion of said second bore, and establish communicationbetween said first intermediate and end portions of said second bore insaid retract position thereof, said elevator spool being configured topermit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, establishcommunication between said first intermediate and end portions of saidthird bore, and establish communication between said second intermediateand end portions of said third bore in said neutral position thereof,permit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, permitcommunication between said first intermediate and end portions of saidthird bore, and block communication between said second intermediate andend portions of said third bore in said low speed position thereof,permit communication between said central portion of said third bore andsaid second and third passages, block communication between said centraland first and second intermediate portions of said third bore, blockcommunication between said first intermediate and end portions of saidthird bore, and block communication between said second intermediate andend portions of said third bore in said medium speed position thereof,and block communication between said central portion of said third boreand said second passage, block communication between said central andfirst and second intermediate portions of said third bore, blockcommunication between said first intermediate and end portions of saidthird bore, block communication between said second intermediate and endportions of said third bore, and establish communication between saidsecond passage and said first intermediate portion of said third bore insaid high speed position thereof.